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Understanding Sensorineural Hearing Loss
Sensorineural hearing loss” is the name we give to the most common type of acquired hearing loss. Making up 90% of cases of hearing loss, sensorineural hearing loss affects the parts of the ear or nerves that transduce (convert) mechanical sound energy into electrical impulses, or transport those electrical impulses to the auditory cortex in the brain.
Basics of Sensorineural Hearing Loss
There are three main parts of our ears: outer, middle and inner. While the outer and middle ear collect and prepare sound to be delivered to the inner ear, the inner ear is where sound becomes electricity, which is what our brains need to receive.
Sensorineural hearing loss is most commonly the result of damage to the stereocilia (tiny, hair-like cells) in the cochlea, the main part of the inner ear. Each of these cells is responsible for transducing a different frequency (pitch) of sound, and when all of their signals are added up and sent to the auditory cortex via the auditory nerves, they give our brains a picture of the sound outside our heads. When our stereocilia become damaged and stop functioning properly, no sound is sent to our brains at those frequencies.
Hidden Hearing Loss
In some cases, even if our stereocilia are intact, we may experience a kind of sensorineural hearing loss as a result of damage to the auditory nerves. This form of hearing loss is often referred to as “hidden hearing loss,” because while it causes hearing loss in the real world, a person who suffers from it can receive a score of “normal” on a hearing test.
Often the result of physical trauma or chemical exposure, hidden hearing loss happens when the myelin sheaths around the auditory nerves are damaged. Myelin sheaths surround all the nerves in our bodies, and keep the signals that travel over those nerves from leaking out. When the myelin sheaths are damaged, some but not all of the information that travels over the nerves leaks out. In the case of our auditory nerves, this means that in a relatively quiet situation, we get enough information from our ears to our brains to be able to hear what’s happening. When the environment starts providing more information, enough of that information will leak out to make it difficult or impossible for our brains to interpret what’s going on.
Causes of Acquired Sensorineural Hearing Loss
“Acquired” means that the hearing loss was not present at birth. Usually, acquired sensorineural hearing loss happens later in life. Some of the reasons a person might develop this kind of hearing loss include:
About half of people over the age of 75 have hearing loss. It’s so common that we tend to associate hearing loss with old age. Age-related hearing loss can begin in a person’s 40s, but we usually don’t notice it until much later when it starts to cause problems in conversation.
Noise-induced hearing loss (NIHL) is also a common type of sensorineural hearing loss. In fact, about 20% of teenagers have measurable hearing loss in one or both ears, probably the result of excessive noise in our modern environments. NIHL can happen slowly over time or all at once from a catastrophic sonic event. While most NIHL is sensorineural, there are some other causes of NIHL that would be considered “conductive” hearing loss; for example, when a sound is so loud that it damages the eardrum or the bones of the middle ear. Vibrations from extremely loud noises can also cause hidden hearing loss.
Illnesses and Medications
Some viral infections—such as measles, mumps and meningitis—can cause sensorineural hearing loss, as can certain cancerous tumors. Similarly, some prescription medicines and life-saving treatments, used only in cases of serious emergency, can cause sensorineural hearing loss.
Head traumas can cause sensorineural hearing loss. Events like car accidents or sports injuries are frequently the source of hearing loss.
Get a Hearing Test
If you suspect you might have sensorineural hearing loss, make an appointment for a hearing test with us as soon as possible. An audiologist will be able to determine what type of hearing loss you have and what the best treatment might be.
Hearing aids are an excellent and important treatment for most types of sensorineural hearing loss, and the technology is getting better and better. Hearing aids today can treat most cases of mild to moderate hearing loss such that hearing ability is restored to near normal and, in some cases, better than normal. Make an appointment today and see what hearing aids can do for you!